Vision correction lenses such as contact lenses and intraocular lenses have been known as commercial products for over 25 years. An acceptable lens must be optically clear, mechanically stable, and must provide sufficient optical correction, gas permeability and wettability to insure that the lens is comfortable and safe during use. Gas permeability is important since the corneal surface of the eye respires by obtaining oxygen and other substances from tear fluid and by releasing carbon dioxide and other products of respiration into tear fluid. The intimate contact and position of the contact lens can substantially prevent the exchange of such constituents between the corneal epithelial cells and tear fluid. As a result the cornea can become starved for oxygen and can accumulate harmful amounts of metabolites within the constituent cells. This can result in corneal edema (swelling) and often extreme discomfort to the wearer. Wettability of the lens is important because a nonwettable lens can be abrasive and irritating to the eye and lid and can cause significant wearer discomfort. A lens must have sufficient mechanical integrity to allow for easy cleaning and handling and maintaining the desired curvature and correction for the individual user. The lens should be immunologically compatible with the eye, reducing chances of allergic reaction or toxic response. Further the lens should be permanently dyeable, easily manufactured and available at low cost.
In the past contact lenses have been made from synthetic polymeric materials such as plastic matrices based on polyacrylate, polymethacrylate, polyhydroxyethylmethacrylate, cellulose acetate butyrate, silicones, etc. More recently contact lenses have been made from collagen, a naturally occurring protein. Miyata, U.S. Pat. No. 4,223,984 is primarily directed to a contact lens made from solubilized defatted transparent crosslinked collagen. Miyata, U.S. Pat. No. 4,260,228 is particularly directed to an improved collagen gel soft contact lens prepared from an aldehyde crosslinked gel containing a polyhydroxy compound such as glucose. Miyata, U.S. Pat. No. 4,264,155 is primarily directed to an improved lens made from collagen gel to which a water soluble organic polyhydroxy polymer has been added.
Ivani, U.S. Pat. No. 4,365,050 discloses and claims certain polymeric aminopolysaccharide compositions used in the fabrication of contact lenses which are limited to graft and block copolymers of an acetyl glycosamine in combination with compounds selected from the group consisting of silicone, collagen, acrylonitrile, acrylamide, methacrylates, alkyl methacrylates, alkyl amino alkylethacrylates, hydroxyalkyl methacrylates, pyrollidones, and vinyl derivatives of pyrollidone.